In general, the dimension of microcapsules typically ranges between 1 and 1000 μm. With the development of microcapsule technology and nanotechnology, the so-called nanocapsules with a size of less than 1 μm, i.e., 1-1000 nm, could also be obtained. Prior to the traditional microcapsules, nanocapsules promise the advantages of: (1) facilitation for further surface modification, increasing embedding rate, and varying distribution or targetability; (2) high stability facilitating processing, storage and transportation; (3) good biocompatibility with little toxicity or side effects; (4) potential for delayed release particles to prolong drug efficacy; (5) exemption from doing harm to other components when used in food. As a matter of fact, nanocapsule technology has been listed as the major R&D high-tech in the 21st century, and nanocapsules have been applied in food condiments, agriculture and biotechnology, biomedicine, cosmetics, textiles and other fields.
Quite a lot works have been reported concerning the preparation of nanocapsules. Zhao et al. (Polymerization Mechanism of Poly(Ethylene Glycol Dimethacrylate) Fragrance Nanocapsules, RSC Advances. 2015, 5(116), 96067-96073) embedded flavor with miniemulsion polymerized nanocapsules without thermosensitivity. Liu et al. (Preparation and characteristics of nanocapsules containing essential oil for textile application, Flavour and Fragrance Journal 2015, 30(4), 295-301) obtained emulsion polymerized flavor nanocapsules just with a embedding rate of 85.4%. Cao et al. (Synthesis of fragrance/silica nanocapsules through a sol-gel process in miniemulsions and their application as aromatic finishing agents, Colloid and Polymer Science 2015, 293(4), 1129-1139) prepared nanocapsules by means of sol-gel method in a reaction system with certain toxicity. Moreover, Hosseinkhani et al. (Novel biocompatible nanocapsules for slow release of fragrances on the human skin, New Biotechnology 2015, 32(1), 40-46) made flavor nanocapsules without thermosensitive release performance with nano-precipitation method. In conclusion, there is no report on the preparation of nanocapsules with good biocompatibility, high embedding rate and controlled release. Nevertheless, the present invention adopts a green, environmentally friendly, simple and mild preparation system to provide nanocapsules with non-toxicity, high embedding rate, temperature sensitivity and controlled slow release performance, which have broad application prospects in the fields of medicine, daily chemicals, textiles, etc.